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Old March 28th 06, 04:16 AM posted to rec.radio.amateur.antenna
 
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Default What kind of antenna is this?


Steve Nosko wrote:
Another consideration is the fact that these are not full half wave
*radiators*, but shortened approx to 66%, or 0.33 lambda (when using this
coax). I


Then that's a big problem.

Unless the outside of the cable has the same Vf as the inside, the
sections won't have the correct phasing.

Phelps Dodge did that two ways.

First, when they used solid dielectric coax, they filled the antenna
with a very thick wax that gave the correct Vf on the outside of the
shield.

Second, when they used air insulated coax inside, they suspended the
coax in air with only an occasional piece of foam for spacing.

There is more to this antenna than just throwing some .66vF sections in
series! Every coaxial collinear I have built and measured from articles
in Ham mags has had virtually no useful gain at zero degrees angle over
a dipole.

73 Tom